/ Washing a new static rope.

Just purchased a new static rope for abseiling into routes in pembrokeshire. I see in the instruction manual it says I should soak the rope and allow it to dry slowly, and that during this process it will shrink by about 5%.
It doesn't say why you should do this or what will happen if I don't.
I don't remember reading this last time I purchased a static rope, but that was quite a few years ago. I certainly didn't do it before.

Used a new static rope without washing and it was very slippy due to the coating - now it's been washed long abseils are slightly less scary.

Also as said above, it means you don't get a nasty surprise if/when the rope shrinks in use (also I suspect a rope shrinking where you have tied knots rigging in a wet cave could pose problems with them over tightening).

Not really surprising, it adds a fairly slow process which makes the rope less pleasant to handle, and often to look at (the dye often runs a bit). A lot of folk prefer a more supple rope at the expense of longevity.